1. Field of the Invention
The present invention relates to an endoscope system that picks up an optical image, which is transmitted by an image guide fiber bundle, by an image pickup device.
2. Description of the Related Art
A video processor that processes video signals obtained from an endoscope is configured to be connected with various kinds of endoscope image pickup apparatuses, if the standards of the endoscope image pickup apparatuses match with the standard of the processor. Such a video processor is connected with what is called a video scope in some cases, and connected with a camera head attached to an eye piece of an optical endoscope in other cases.
Specifically, Japanese Patent Application Laid-Open Publication No. 2001-70240 discloses a technique for enabling endoscope image pickup apparatuses for various purposes of use to be connected with a common video processor. The publication recites, for example, an endoscope image pickup apparatus in which an image pickup apparatus that picks up an image of an object and obtains a video signal is detachably connected to an endoscope that obtains an image of an object as an optical image.
The optical endoscope that obtains the optical image of the object has a structure for transmitting the optical image obtained from the distal end portion of the insertion portion to the rear end portion of the insertion portion by an image guide, and when the optical endoscope is a fiber scope, for example, a fiber bundle configured by binding a plurality of optical fibers is used as an image guide.
When a camera head is connected to an eye piece of such a fiber scope to perform video observation through a video processor and a monitor, a moiré fringe pattern is sometimes generated by an interference between the mesh pattern of the fiber bundle (mesh pattern generated by binding the optical fibers) and the pixels of the image pickup device of the camera head. In addition, the same is true on a hybrid scope, i.e., a scope of a type in which an optical image is transmitted from the distal end to the proximal end of the insertion portion by a fiber bundle and the transmitted optical image is picked up by an image pickup device provided at the proximal end portion of the insertion portion.
In order to address such a case, conventionally, observation has been performed at a focus position at which moiré is not distinct by shifting the focus of the optical system or observation has been performed by turning off the enhancing function in the video processor by manual operation in order to prevent the moiré from being enhanced.